1. Field of the Invention
The present invention concerns surgical devices for repairing bone fractures or dislocations.
2. Discussion of the Known Art
Traumatic separation of the acromioclavicular (AC) joint is common, particularly among athletes. Complete rupture of the coracoclavicular ligament is common in the more severe grades of injury (type 3 or greater). Although surgical techniques for repairing or reconstructing the ligament have evolved over the last several decades, a gold standard has not yet emerged.
The proper course of initial treatment of an acute type 3 separation of the AC joint remains controversial. Although studies have demonstrated successful outcomes with nonoperative treatment, others have noted poor outcomes in over 40% of patients. Many of these patients have subsequent surgical treatment for ongoing symptoms of both pain and/or weakness. Long-term follow-up has shown residual symptoms in most patients treated nonoperatively. This has led to a commonly accepted recommendation of surgical treatment in high-level athletes or high-demand manual laborers. But even among patients with lower demand levels, a recent study has shown a poor outcome in 20% of non-athletes, and an additional 15% of patients reported significant symptoms of weakness.
The weight of the arm places a constant deforming force on a surgical fixation construct during biologic healing. In the acute setting, there is a robust healing response after ligament rupture, and additional grafting may not be necessary as long as the initial fixation can remain stable during the healing process. In the chronic setting, it is necessary to add biologic graft material to the fixation construct to ensure long-term stability and function. During the healing process, graft material is likely to weaken and stretch during the course of revascularization. Thus, when a fixation device is used in conjunction with a graft, it is at risk for implant failure if the graft deforms and stretches.
Surgical treatment has shown higher success rates in recent studies, but many of the techniques have become associated with significant implant related complications. Failure to establish a treatment with a reproducible outcome and a consistently low complication rate has therefore led most sports medicine specialists to continue to recommend non-operative management for the initial treatment of type 3 AC joint separations. For example, in a recent survey of over 500 members of the American Orthopaedic Society for Sports Medicine, more than 80% of respondents preferred non-operative treatment for initial management.
Prior techniques using various forms of hardware fixation, such as the Bosworth screw, have fallen out of favor because of hardware failures and the need for a second procedure to remove the hardware. The Weaver-Dunn procedure, first described in 1972, avoids the use of metallic implants and continues to be popular notwithstanding an originally reported failure rate of 28% in a small series of 15 patients. Attempts to improve the original Weaver-Dunn technique have involved various methods of non-metallic fixation to stabilize the AC joint. Notwithstanding the success of these methods, implant-related problems including infection, soft tissue reactivity, and fractures have been identified. These implant-related problems have led to development of purely biologic constructs that use allograft or autograft to reconstruct the coracoclavicular complex.
Biomechanical studies have yielded techniques for re-creating the native anatomy more accurately, and finding materials that can tolerate cyclic loading without deformation or failure. The ultimate strength, stiffness, and load elongation curves of the native complex have been measured against various repair constructs, and testing has been performed with both simple load to failure modes as well as response to cyclical loading to simulate postoperative conditions. Traditional procedures like Weaver-Dunn have been shown to be much weaker and more compliant than the native ligament, thereby explaining the frequently observed high failure rate of that procedure. A common modification involves stabilizing the joint by placing a cerclage material around the base of the coracoid and through a hole in the clavicle. Thick, robust materials such as polidioxanone bands or large tendon grafts have shown comparable strength relative to the native complex; however, their load-elongation curves indicate lower stiffness in most of the tested materials. Significantly, cerclage techniques have also been found to be non-anatomical as the fixation method drags the distal clavicle anteriorly. One study showed that even when the drill hole is placed within 2 mm of the anterior edge of the clavicle, the clavicle is pulled anteriorly. This malreduction is likely to lead to abnormal forces placed on the construct, weakening the construct with time as cyclical forces act on it constantly during the healing process.
Fixation placed in anatomically correct positions should improve implant stability and response to cyclical loads. Techniques have been described that achieve stability by placing grafts or fixation devices through anatomically placed boles in the clavicle and coracoid. An ideal procedure would use a fixation construct that not only restores the normal biomechanics of the ligament complex, but also maintains reduction throughout the biologic healing process.
U.S. Pat. No. 5,645,588 (Jul. 8, 1997), incorporated by reference, shows a graft attachment device for use arthroscopically to reconstruct the anterior cruciate ligament (ACL) in the knee. The device has a rectangular, bar-shaped body of stainless steel or equivalent biocompatible material, 4 mm in width and 12 mm in length. A first pair of 0.062 inch diameter openings are formed near the opposite long ends of the device body, and a second pair of 0.78 inch diameter openings are formed along the long direction of the device body between the first pair of openings. A patellar tendon graft is linked to the device by two sutures both of which pass through the second pair of openings in the device, and the free ends of each suture are tied so that sutures form closed loops. Each one of a second pair of sutures passes through a corresponding one of the first pair of openings, and the free ends of the second pair are threaded through a slot at the end of a pin instrument that has been inserted though passages formed in the femur and the tibia. The device, together with the graft which is linked to the device, are pulled through the passages by the pin instrument until the device emerges from a passage at the upper femoral cortex. The device is then rotated and seated against the femoral cortex. See also U.S. Pat. No. 6,533,802 (Mar. 18, 2003), and U.S. Pat. No. 5,041,129 (Aug. 20, 1991), both of which are incorporated by reference.